Im going to take the opposite position. I said this in another thread recently.....my first cruise was last November on the Dream. We sprung for 4A and were booked on deck 10...that is, until I read (here actually) about the noise from the pool deck. To play it safe, I dropped us into a stateroom on deck 9. I will never be able to tell you if the noise from deck 11 was a problem on deck 10....but I've read enough complaints that it is (and an equal amount that says it isn't - I just wasn't willing to take the chance considering the cost of cruising)
However, when we first walked into our room on deck 9 last year, I was instantly reassured that I made the right choice. To me, the overhang is a significant drawback and on deck 10 it will block your view of the sky. Yes, it will provide shade. But you will not be able to see the stars or a large portion of the sky from your veranda. To me, the stars (which I don't remotely see enough of in light-polluted Long Island) are more important than some shade. That's why we have sunglasses!
Regardless, I'm sure both deck 9 and deck 10 will be good choices. You just have to decide whether a better viewing angle of the sky is important to you. It was to me.
Just some random thoughts. There's no difference in cost between deck 9 and 10. They're both 4a. Also, afaik, all of the category 4's are deluxe family verandas. The difference between a and e is the deck you're on. 4a is deck 9&10, 4b is deck 8, 4c is deck 7, 4d is deck 6 and 4e is deck 5. So the size of the room won't change, just how high up you are. 9 is quite high. So's 8. Even 7.
Also, don't forget the importance of where your room is on the deck. How close are you to the elevators? How close are you to high traffic areas? If you're on deck 10, do you want to be under cabanas or the pool deck? (I'm guessing here, but a room on deck 10 that's under the adult section (Closer to the bow) might be quieter...
sorry, deleted comment
